Fire damper



F. J. M CABE Sept. 20, 1966 FIRE DAMPER 5 Sheets-Sheet 1 Filed June 17,1964 INVENTOR.

FRANCIS J. Mc CABE ATTORNEY Se t. 20, 1966 F. J. M CABE 3,273,632

FIRE DAMPER Filed June 17, 1964 5 Sheets-Sheet 2 54 W l. I

I W l:

I I v :3 INVENTOR. o 49 BY FRANCIS J. McCABE 4e moms/s. 2W4

ATTORNEY F. J. M CABE FIRE DAMPER Sept. 20, 1966 5 Sheets-Sheet 3 FiledJune 17, 1964 TOR.

' FRANCIS J. MCCABE WWW ATTORNEY Sept. 20, 1956 cc 3,273,632

FIRE DAMPER Filed June 17, 1964 5 Sheets-Sheet 5 Figs i4 F79. l5

89 INVENTOR.

FRANCIS J MCCABE ATTORNEY instant invention.

United States Patent "ice 3,273,632 FIRE DAMPER Francis J. McCabe, PennsPark, Pa., assignor to Air Balance Inc., Philadelphia, Pa., acorporatlon of Pennsylvania Filed June 17, 1964, Ser. No. 375,855 17Claims. (Cl. 160-1) This invention relates generally to fire damperconstructions, and more particularly, relates to automatically actuatedfire damper structures adapted for installation in air delivery systemssuch as duct structures and which include a plurality of hingedlyinterfitted metal slats of novel configuration which afford easyrelative rotation between adjacent slats without binding.

In the past, fire dampers or fire shutters have been designed for thesame general purpose as that of the However, the hinging structures ofthe slats utilized in such known devices have taken the form ofinterfitted circular arcs, or interfitted identical spirals, neither ofwhich configurations permit 180 relative rotation between adjacent slatsof the composite damper structures. Consequently, the slat structurescan not be compactly reversely folded against one another to form asmall and unobstrusive structure. In contrast to these known types ofdevices, the fire damper construction according to the instant inventionutilizes a hinging configuration of irregular shape which permitssubstantially 180 rotation of adjacent slats and thereby makes possiblean extremely compact slat assembly which occupies a minimum of space.Accordingly, it is a primary object of this invention to provide a novelfire damper slat or blade having parallel spaced apart longitudinallyextending edges each of which is differently formed but complemental tothe other to provide one half of a blade hinging structure in which oneof the edges may he slipped endwise into the complementally formed edgeon another blade of the type formed at its own opposite longitudinallyextending edge, each of the half hinge edges including curved andstraight regions which conjointly function to provide substantially 180relative rotation between adja cent hinged together blades without bladebinding or any tendency toward blade disengagement, the center ofrotation of the composite hinge structure being spaced laterally fromthe centroid thereof.

Another object of my invention is to provide a novel damper constructionin which the rotation of the damper slats to effect closing of thedamper unit is carried out by positively acting drive meansautomatically rendered operative by a predetermined temperaturecondition in the region of the fire damper.

A further object of my invention is to provide a novel fire damperstructure which is fabricated in modular form so that it may be utilizedwith different types of mounting flange configurations securablethereto.

Yet another object of my invention is to provide a novel fire damperslat construction, and complete fire damper assemblies utilizing suchnovel slat, wherein the slat hinging configuration is characterized byan axis of rotation which is generally disposed laterally of the mainplane of the slat.

The foregoing and other objects of my invention will become clear from areading of the following specification in conjunction with anexamination of the appended drawings, wherein:

FIGURE 1 is a front elevational view of a fire damper structureaccording to the invention with the right hand portion broken away, thedamper structure being illustrated with the blades in compact foldedform to permit passage of air therethrough;

FIGURE 2 is a vertical cross sectional view through Patented Sept. 20,1966 the damper construction of FIGURE 1 as would be seen when viewedalong the line 22 thereof, phantom showings being also illustrated asdesignating the positions of the damper blades when the latter have beenvertically expanded to close the damper opening;

FIGURE 3 is a horizontal cross-sectional view taken through the firedamper structure of FIGURE 1 as would be seen when viewed along the line3-3 thereof;

FIGURE 4 is a front elevational view of the fire damper of FIGURE 1modified to illustrate the damper blades in vertically opened outposition as would be seen when the damper structure has been actuated tocut off air flow therethrough;

FIGURE 5 is a horizontal cross-sectional view through the damperstructure of FIGURE 4 as would be seen when viewed along the line 5-5thereof;

FIGURE 6 is a modified form of fire damper structure in which the damperblades are compacted upward into a hat structure to remove the same fromthe air flow path through an air duct structure illustrated in phantom,the fire damper structure being shown in perspective with portionsbroken away to reveal constructional details thereof;

FIGURE 7 is an enlarged fragmentary vertical crosssectional view throughthe upper portion of the modified form of fire damper shown in FIGURE 6;

FIGURE 8 is a perspective showing somewhat similar to that of FIGURE 6but in which the damper blades have dropped as a curtain to block airflow through the damper and duct structure;

FIGURE 9 is a perspective view of a modified form of fire damperconstruction similar to that of FIGURE 6 but in which the damper unit isdisposed completely within a duct structure and is not provided with thetop cap construction;

FIGURE 10 is a plan view of another modified form of fire damperintended for disposition in a horizontal plane to close a verticallyextending air passage when actuated;

FIGURES 11 and 12 are vertical sectional views, on an enlarged scale,taken through the modified form of fire damper shown in FIGURE 10 aswould be seen when viewed along the lines 1111 and 1212, FIG- URE 11representing the damper when open while F-IG- URE 12 represents thedamper with the blades opened out in damper closing position;

FIGURE 13 is an end elevational view of one of the damper blades shownon an enlarged scale illustrating the asymmetric configuration of thehalf hinge configuration formed at the opposite parallel longitudinallyextending blade edges;

FIGURES 14 through 19 illustrate on an enlarged scale a pair of hingedlyinterfitted damper blades at successive points of relative rotationcorresponding to fully compacted to fully expanded conditions of thedamper blades.

In the several figures, like elements are denoted by like referencecharacters.

Considering first FIGURES 1 through 5, it is observed that the firedamper structure includes a frame assembly designated generally as 30which carries a blade assembly designated generally as 31. The frameassembly includes a top member 32 and bottom member 33, a pair ofidentical opposite side frame members 34 rigidly secured at their upperand lower ends to the top frame member 32 and bottom frame member 33 asby welding to thereby form a fixed rectangular frame. The top and bottomframe members 32 and 33, as best seen in FIGURE 2, are of the samecross-sectional configuration and are arranged in the frame assembly asmirror images, these members being formed of sheet metal stockconvoluted to form a central width-wise extending channel defined bysloping side walls and a pair of flanking widthwise extending frontand/or back channels of generally rectangular cross-section.

The central channel of the bottom frame member 33 is defined by thedivergingly upwardly extending wall portions 35 while the front aud/ orrear flanking rectangular channels are defined by the orthogonallydisposed wall portions 36, 37 and 38, the upper ends of the wallportions 38 being turned horizontally inward toward one another inpartially overlying relationship to the wall portions 37 to provideflanges 39. Since the top member 32 is exactly the same incross-sectional shape as the bottom frame member 33 and differs from thelatter only in that it is oriented in inverted position, thecorresponding Walls and flanges of the top frame member 32 aredesignated by the same corresponding reference characters to thoseutilized for the frame bottom member. That is, the wall portions aredesignated by the numerals 35 through 38 and the flanges are designated39. The sloping side wall portions 35 of the top and bottom framemembers 32 and 33 respectively act as guides or lead-ins for the ends ofthe upper and lower terminal edges of the damper blades to preventwedging or jamming thereof when the blades are expanded to opened outform to close the cross-section of the fire damper, the disposition ofthe upper edge of the upper blade and the lower edge of the lower bladebeing as illustrated in phantom in the showing of FIGURE 2.

The side frame members 34 are each formed from a pair of verticallyextending parts of constant cross-sect-ion of the form best seen in theshowings of FIGURES 3 and with these side frame member parts beingdesignated generally as 40 and 41. The part 40 is formed from a piece ofrectangular sheet metal stock having its long side edges turned in thesame direction at right angles to the main plane of the stock to formcorner flanges 42, and the vertically extending central region of themain planar portion is folded forward in the same direction as thecorners 42 to form the vertically centrally extending U-shaped channel43 having side walls parallel to the corner flanges 42 and a connectingwall parallel to the main plane of the member 40. The side frame memberpart 41 is a vertically extending sheet metal part formed into aU-shaped channel member having a laterally outwardly turned flangeextending from the upper end of each of the channel side wall portions,which flanges are seated flat-wise against the inside surface of theside frame member part 40 on opposite sides of the channel portion 43 ofthe latter, and the bottom wall of the U- shaped channel part 41 isseated against the bottom wall of the U-shaped channel, part 43 of theside frame member part 40. The frame parts 40 and 41 are fixedly securedtogether, as by spot welding, along their engaged surfaces.

The U-shaped channel part 41 of the side frame member is shorter inlength than the side frame part 40 and terminates at points above thelower edge and below the upper edge of the latter, so that the top andbottom frame members 32 and 33 are disposed respectively below and abovethe channel part 41 and in end abutment with the side frame member parts40. The upper and lower ends of the side frame part 41 engagerespectively the junction of the walls 35 and 36 of the top and bottomframe members 32 and 33 while the opposite ends of the top and bottomframe members are close fittingly disposed between the corner flanges 42of the side frame member part 40.

It is observed that the frame assembly may be inverted top for bottomwithout in any manner-changing its appearance, so that while the topframe member 32 functions as a head member and the bottom frame member33 functions as a sill member, the head and sill members are in factinterchangeable since they are indistinguishable and the fire damperassembly therefore has no real top or bottom. The bottom channel wall ofthe U-shaped channel member 41 of the side frame members 34 functions,as will be subsequently seen, as a blade guide and will be so referredto hereinafter, Before considering the blade assembly 31 in detailattention should be directed to the blade follower mechanism carried bythe frame assembly, the details thereof being most clearly observed inthe showings of FIGURES 2, 3 and 5.

Each of the blade follower assemblies situated at the opposite sideedges of the frame assembly includes a pair of blade follower elements44 extending vertically between the top and bottom flanges 39 of thehead and sill members 32 and 33, and a pair of blade follower closurecoil springs 45. The blade follower elements 44 are each formed from apiece of rectangular sheet metal having one longitudinally extendingvertical edge rolled into a loop as at 46, and having its otherlongitudinally extending vertical edge turned at approximately a rightangle to the main plane of the blade follower and folded back uponitself to form a reinforced bearing edge 47 which abuts the hinged edgesof the blade assembly 31 in the manner illustrated in FIGURES 2 and 3.Each of the blade followers 44 is secured for swinging motion about avertical pivotal axis by means of the pivot pins 48 extended through thehead and sill flanges 39 into the rolled loops 46 formed at one edge ofthe blade follower as previously described.

The closure coil springs are each formed with a pair of end loops 49rolled outward away from one another to provide a fairly flatintermediate portion 50 which is riveted or otherwise fixedly secured asat 51 to the outside of the side frame member part 40. The natural rollof the spring loops 49 tries to move the loops toward one another sothat they each bear against the outside surface of one of the bladefollower elements 44 to force the reinforced bearing edges 47 againstthe blade assembly 31 as seen in FIGURES 2 and 3. When the bladeassembly opens out in the manner shown in FIG- URES 4 and 5, the springloops 49 of the closure springs 43 swing the blade follower elements 44about their pivot pins 48 to drive the reinforced bearing edges 47inward into engagement with the blade guide face of the U-shaped channelelement 41 forming part of the side frame members 44 to thereby lock theblades of the assembly 31 in their vertically opened out position andinsure that the opening through the fire damper frame assembly remainscompletely closed.

Consider now the blade assembly 31 illustrated in FIGURES 2 and 4 ascomprising five individual damper blades pivotally connected togetheralong parallel horizontally oriented longitudinally extending edges, theblades being designated from top to bottom in the assembly as blades 52through 56. All of the blades are of the same length and have theiropposite ends disposed in close proximity to the blade guide faces ofthe side frame U-shaped channels 41, the center blade 54 having securedthereto a pivot pin 57 at each end of the blade with the pivot pinprojected freely rotatably through the blade guide face of the sideframe channel member 41 and base of the U-shaped channel portion 43 ofthe side frame member 40. This pivot pin arrangement, of course,supports the entire blade assembly 31 from the side frame members 34 ofthe frame assembly 30, the blades 52 through 56 being secured togetherin central position by means of the cinch cable 58 wrapped thereaboutand secured by a fire link 59.

The fire link 59 is formed from a pair of metal plates held together bya low temperature fuse metal chosen to melt at a desired temperature.Disposed between the blades 52 and 53 and fixedly secured to one ofthem, and also disposed between the blades 54 and and fixedly secured toone of these are generally C-shaped actuating springs 60 illustrated inthe showing of FIGURE 2 in their compressed form and held in such stateby the cinch cable 58 and fire link 59. When the fuse metal of the firelink 59 melts, thus relieving the restraint upon the acdrive the damperblades away from one another both upwardly and downwardly by asuflicient amount to allow the closure coil springs 45 to swing theblade follower elements 44 inward into positions where the latterdevelop sufficient torque on the blades to completely drive the latterinto the vertically disposed condition shown I in FIGURES 4 and 5.

As best seen in FIGURE 4, the hinging structure of the damper blades issuch that air blowing against the plane of the damper assembly cannotpass therethrough. Moreover, as is most clearly seen in FIGURE 5, thevertically extending position of the reinforced bearing edges 47 of theblade follower elements 44 is such as to close the small opening betweenthe blade guide face of the side frame member 41 and the ends of theblades 52 through 56 so that the actuated or closed damper is for allreal purposes substantially air tight. From FIGURES l and 4 it isobserved that the blade assembly 31 is approximately centered in theframe assembly 30 and that closure coil springs 45 are spaced above andbelow the blade assembly at each side thereof. Other arrangements are ofcourse possible, as for example, the blade assembly 31 may be pivoted ata vertically higher point in the frame assembly by merely securing thepivot pin structures 57 to damper blade 53 instead of blade 54.

Before considering in detail the novel damper blade structure as shownin FIGURE 13 and the method of operation as illustrated in FIGURES 14through 19, attention should be directed to the damper structuremodifications shown in FIGURES 6 through 12 since all forms of thedampers utilize the same novel damper blade in the same manner. Considerfirst FIGURES 6, 7 and 8 which illustrate a gravity operatedvertical-drop fire damper structure providing a substantiallyunobstructed air flow cross-section through a duct system. The damperassembly includes a frame assembly designated generally as 61, a bladeassembly designated generally as 62, and a mounting assembly designatedgenerally as 63.

The frame assembly 61 is formed from four lengths of channel stockarranged in a rectangle with the flanges presenting toward one anotherand rigidly secured at the corners, as for example by welding, theopposite side members of the frame assembly being designated as 64 whilethe top and bottom frame members are designated respectively as 65 and66. The width of the channel shaped frame members as measured betweenthe channel flanges is slightly larger than the front-to-back width ofthe blades assembly 62 so that the latter fits fairly closely betweenthe flanges of the frame side members 64, and the length of the bladeassembly 62 as measured from side to side of the fire damper unit isjust slightly less than the distance between the inside surfaces of theframe side members 64 which form the side walls of the frame assembly61.

The blade assembly 62 is compactly reversely folded to form a bladestack of the type previously seen in the showings of FIGURES l and 2,and this assembly is pivotally secured within the frame assembly 61 atthe upper end thereof by means of pivot shaft 67 carried by the upperblade of the blade assembly 62, the pivot shaft 67 being projectedthrough the frame side members 64 so that the blade assembly may openout by unfolding downward as a curtain in the manner best seen in theshowing of FIGURE 8. The blade assembly 62 is secured at the upper endof the frame assembly 61 by means of the cinch cable 68 and fire link69, the cinch cable 68 passing throughthe side flanges of the frame topmember 65 just above the blade assembly itself. The blade assembly 62 isgravity actuated when the fire link 69 opens due to the occurrence ofthe predetermined high temperature condition, drop assistance beingprovided by the bar weight 70 secured to the lowermost blade of theblade assembly 62, as for example is seen in the showings of FIGURES 7and 8.

The mounting assembly 63 consists of a flat rectangular bottom plate 71,a pair of opposite flat side plates 72 and a top cap or head 73. The topcap 73 is of inverted U-shape or channel shape, having a channel basewall 74 seated flat-wise upon the upper surface of the frame top member65, and having side walls 75 extending downward in 'front of and behindthe frame assembly 61 for a distance substantially equal to the verticaldepth of the compacted blade assembly 62, the side walls 75 being turnedhorizontally outward away from the frame assembly 61 at both the frontand the back thereof to form the flanges 76. The upper ends of thesideplates 72 are cut away at the upper corners to conform to the crosssectional shape of the top cap 73, all of the mounting assembly membersbeing fixedly rigidly secured to one another at their meeting edges andbeing secured,

as by spot welding, to the flat planar surfaces of the frame assemblyagainst which they are flatwise disposed. The bottom plate 71, sideplates 72 andflanges'76 of the top cap 73 are provided with a pluralityof mounting holes 77 spaced apart peripherally thereabout so that thedamper unit may be fixedly secured to the duct system within which it ispositioned, as for example to the ends of the ducts 78 shown in FIGURE 7in fragmentary form and in phantom in FIGURES 6 and 8.

The fire damper assembly of FIGURES 6, 7 and 8 is observed to be one inwhich the height of the frame assembly 61 is greater than the height ofthe duct system by an amount sufficient to allow the blade assembly 62to be positioned in its folded compacted form upward out of the duct airstream and to thereby avoid presenting an apparent restriction in theduct cross-sectional area, the mounting assembly 63 elfectivelypreventing any appreciable air leakage at the joint of the duct system.

The damper structure illustrated in FIGURE 9 differs from that shown inFIGURES 6, 7 and 8 only in that the mounting assembly 'thereof is formedfrom flat rectangular top and bottom plates 79 and side plates 80, andis mountable completely within the associated duct work Without anyprotruding upper part corresponding to the region of the top cap 73. Ofcourse, the blade assembly 62' necessarily extends downward partly intothe air flow cross section of the duct in this particular form ofstructure. The frame assembly and blade asembly of the structure shownin 'FIGURE 9 correspond of course to those of FIGURES 6, 7 and 8, andare therefore designated by primed reference characters forcorresponding parts. The frame assembly and blade assembly of the firedamper constructions shown in FIGURES 6 through 9 may therefore beconsidered as a modular structure of desired height and width to whichmay b secured a particular desired type of mounting assembly as may bedetermined by the specific installation.

While the showings of FIGURES 6 through 9 are d'irec ted toward firedamper modular structures intended for positioning in a vertical planewithin a duct structune and are thereby enabled to utilize the force ofgravity to unfold the blade assembly, the gravity actuation of the bladeassembly is not possible when the damper unit must be positioned so thatthe blade assembly is in a horizontal plane when opened out to close thecrosssection of a vertically running duct. The blade assembly of ahorizon-tally disposed damper structure requires a positive actuationdevice, one form of such a structure being illustrated in the showings 0f FIGURES 10 through 12 to which attention should be now directed.

The frame assembly in FIGURES 10, 1 1 and 12 is the same as that ofFIGURES 6 through 9 and is therefore designated 61a. 'Ilhe bladeassembly being similar to that also previously described is designated62a, and its associated cinch cable and fire link and pivot shaft arerespectively designated as 68a, 69a and 67a. The blade assembly 62adilfers from the previously described assembly of FIGURES 6 through 9 inthat the bar weight 70 normally secured to the bottom blade of theassembly has been eliminated. In its stead -there have been secured tothe blade next to the fire link, designated as 1, a pair of hooks 82secured as by means of the nuts P3 to the blade 81 proximate theopposite ends of the atter and between the side walls of the channelshaped 'rame side members 64a. Secured to each one of the IOOkS 82 isone end of a constant tension spiral spring 14 which extends between theside walls of the frames .ide members 64a to a take-up spool '85 mountedupon in L-shaped bracket 86 secured as by rivets 87 to one aide wall 88of the frame member 66a. The take-up pool 85 is so positioned by meansof the bracket 86 :hat the free end of the blade 81 may readily moveinto ihe frame member 66 under the spring and take-up spool 35 in themanner most clearly seen in the showing of FIGURE 12.

The constant tension spiral extension spring '84 is made of flat stripmaterial and may be of the type marketed by Hunter Spring Company ofLansdale, Pennsylvania, under the trade name Negator, these springsexerting the same pulling force on the blade assembly when the latter isin the position shown in FIGURE 12 as when the blade assembly is in thecompacted form shown in FIGURES 10 and 11. The fire damper moduleintended for horizontal plane disposition and illustrated in theshowings of FIGURES 10 through 12 may be provided with any convenienttype of mounting assembly for installing the damper structure in an airflow system.

Those aspects of the fire damper structures illustrated in FIGURES 1through 12 which have been thus far described in detail have related tothe framing, mounting and actuating portions of the composite damper,and have presupposed blade assemblies 31, 62, 62' and 62a as beingoperative. 'Dhe operability of the blade assemblies is of coursecritically dependent upon the interfitted hinging relationship of theblades to one another, and

a better understanding of this action is best obtained from aconsideration of FIGURES 13 through 19. FIG- URE 13 illustrates thesomewhat unconventional configuration of the blade edges which form thehinging structures, while FIGURES 14 through 19 illustrate the relativepositions of the blades hinging edges as a pair of blades are rotatedrelatively to one another through substantially 180, FIGURE 14corresponding to the compacted or folded condition of a blade assembly,while FIGURE 19 corresponds to the opened out or fiat curtain conditionof the blade assembly.

Referring first to FIGURE 13, it is observed that the blade is formedfrom a planar web of thickness 2 which is designated by the referencecharacter W, and which has formed at its opposite ends the hinge edges89 and 90, the edge 89 *forming the inside portion of the hingeStructure and the edge 90 'forming the outside portion of the hingestructure, all as shown in the views of FIG- URES 14 through 19. Theinside hinge section 89 and the outside hinge section 90 are bothsubdivided into curved and straight regions each of which is designatedby alphabetic reference characters, the curved regions A, -B and C ofsection -89 and the curved regions AA, 'BB and CC of section 90 allbeing in the form of circular arcs. The circular arc sections A and Care generated about the center point X1 while the circular arc B isgenerated about the point X2 in the inside hinge section 89. Similarly,the arcs AA and CC are generated about the point Y1 as a center whilethe circular arc BB is generated about the point Y2.

The points X1 and X2 lie on a line which is parallel to the sides of thestraight section S, with these points being separated by the length ofthe section S which joins the circular arc section A to the circular arcsection B. The points Y1 and Y2 of the outside hinge section 90 aresimilarly located with respect to the curved sections AA, BB andintervening straight section SS. The section I in the outside hinge edge90 is a short transition or joining section which permits the smoothjoinder of the ends of curved sections BB and CC, the transition sectionbeing generally so short as to be visually unobservable. The bingeterminating sections D and DD are substantially straight with theopening defined between the curved section A and straight section Dbeing somewhat greater than the thickness 1? in order to allow theentrance therebe-tween of the end of curved section AA, as is mostclearly seen in FIGURES 15 and 16. The opening defined between the endof curved section AA and straight section DD of the outside hinge edgeis somewhat greater than twice the thickness t of the blade material butwill be more generally determined by the length of section S, as alsoibest seen in FIGURES 15 and 16, and which will become clear as thedescription proceeds.

It should be noted that the center of the hinging rotation is identifiedas X1Y1 in the rotational views of FIGURES 14 to 19 because the pointsX1 and Y1 of the inside and outside hinge sections 89 and 90respectively become coincident when the hinge sections are intenfitted.It should also be observed that the center of rotation points X 1 and Y1are considerably laterally ofiset from the centroids of the respectiveinside and outside hinging sections 89 and 90. The need for such acentroidal offset will become clear as the description progresses,although prior to the instant invention this fact had never beenrecognized and attempts were consequently made to fashion hingingstructures from circular or spiral configurations in which the centroidwas placed at the axis of rotation. These latter types of configurationswill function so long as the hinging range is restricted toapproximately 90, but any attempt to utilize such structures forrotation approaching 180 results in .a condition wherein the interfittedblades either fall apart on the one hand or become bindingly engaged onthe other hand.

Referring now first to FIGURE 14 which illustrates the folded conditionof a blade assembly, and consequently one of the extreme positions ofthe adjacent blades, assume that only the circular curved sections A andAA of hinging sections 8-9 and 90 exist, and that the remainder of theinside and outside hinge configuration have not as yet been generated.With the foregoing in mind refer now to FIGURE 19 which illustrates theother extreme position of the adjacent blades and which shows thatcircular curved section A has been rotated about center X*1Y1 in -aclockwise sense through approximately In order that the web sections W1and W2 achieve a parallel planar relationship, it is necessary that thecurved section A be joined to the web section W2 by a structure whichdoes not mechanically intersect the curved section AA. This is bestachieved by extending one end of the curved section A in a straight linepast the tip of the curved section AA, as illustrated by the straightsection S, and then to follow around the outside contour of the sectionAA by adding the curved sections B and C. This procedure automaticallyestablishes sufiicient clearance distance between the end of curvedsection A and sections D or C to permit the rotational movement ofsection AA, this opening distance being as before indicated somewhat inexcess of the thickness t of the blade stock.

Now, with sections A, S, B and C of the inside hinge section 89established in the manner just described, this just generated structuremay be rotated counter-clockwise to move it back into the position shownin FIGURE 14. Sections SS, BB and CC may now be added to the end ofsection AA of the outside hinge portion 90 by following around thecon-tour of the previously generated inside hinge section 89. Sufficientclearance is of course maintained between the inside and outside hingingsections 89 and 90 as is shown in the figures. The terminating sectionsD and DD connect the flat planar web portions W to the now generatedhinge sections. The angle between the webs W1 and W2 in FIGURE 14follows from the nature of the compacted reversely folded blades, as forexample is most clearly seen in the showing of FIGURE 2 illustratingsuch a reversely folded compacted blade assembly. Obviously, for a givengauge of metal from which the blades are formed, the angle between theweb portions of the adjacent blades decreases as the length of the web Wincreases between the inside and outside hinging portions 89 and 90 of agiven blade since the size of the hinging structures is independent ofthe web length and depends only upon the thickess t of the bladematerial and the radius of curvature of the curved portion A of insidehinge section 89.

The 180 extent of curved section A derives from the fact thatapproximately 180 of rotation between adjacent blades is desired. Theangular extent of section AA of outside hinge section 90 need not be 180to maintain contact with section A, and in fact cannot be such in anyphysically realizable structure. The resection or cut back on theangular extent of curved section AA is readily determinable from FIGURE19 after the rotation of curved section A and the addition of straightextension S, the inside bounding edge of the straight section Sdetermining the maximum extent of curved section AA which will preventintersection thereof with the portion S. Consequently, the end of curvedsection AA cannot be rotated beyond the point indicated in FIGURE 19without coming into positive abutment with the straight section S, andhence, a positive stop action between adjacent blades results when thedesired degree of rotation has occurred. It should be appreciated,however, that curved section AA cannot be resecte'd back arbitrarily,but such cut back is limited to that which will still prevent fall apartor disengagement of the hinging sections in the rotational positionshown in FIGURE 17 for example.

The resultant previously described hinging structure exhibits a compoundtype of interfit which may be separated into two specifically differentforms. One form of such interfit is clearly observed in FIGURES 14 and15 as being of the type generally known as head and socket. FIGURES 17,18 and 19 illustrate what might best be characterized as a laminar entrytype of motion in which the curved end section AA slides into the insideof the hinge section 89. FIGURE 16 illustrates a transition region inwhich the relationship between the hinging parts 89 and 90 is partlythat of the head and socket arrangement and is also partly that of thelaminar entry structure. The angular relationships between the webs W1and W2 in FIGURES 15 through 18 are respectively 90, 120, 163 and 170,the 163 showing of FIGURE 17 illustrating the point of completedeparture from any semblance of a head and socket arrangement betweenthe inside and outside hinge parts 89 and 90.

Having now described my invention in connection with particularembodiments thereof, it will be clear that modifications and variationsthereof may now occur from time to time to those persons normallyskilled in the art without departing from the essential scope or spiritof my invention, and accordingly it is intended to claim the samebroadly as well as specifically as is indicated by the appended claims.

What is claimed to be new and useful is:

1. A fire damper assembly comprising in combination,

(a) a rigid rectangular frame including top, bottom and opposite sidemembers which define a main frame plane common to all of said frameforming members and transverse to the air flow path through said frame,

(b) a blade assembly including a plurality of individual damper bladesadjacent ones of which are pivotally interconnected by interfittedhinging elements carried by parallel longitudinally extending bladeedges, the axis of pivotal rotation of said interfitted hinging elementsbeing offset from the centroids of each of said hinging elements toeffect substantially 180 relative rotation between adjacent blades,

(ic) pivot means carried by one blade of said blade assembly andsupported by said frame mounting said blade assembly in said rectangularframe,

(d) means securing the blades of said assembly reversely folded oneagainst another to form a compacted assembly characterized by thedisposition of the hinge assemblies in planes substantially parallel tothe said main frame plane, said securing means including a bindingelement and a temperature responsive fusible link disposed about saidblade assembly, and

(e) means elfective to cause said blade assembly to unfold and close theair flow path through said frame by effecting relative rotation betweenadjacent blades of saidassembly of substantially when said securingmeans is rendered inoperative.

2. A fire damper assembly as set forth in claim 1 wherein,

(a) said blade assembly pivot means is carried by the free hingingelement of one end blade of the said blade assembly, and which pivotmeans is supported by said frame opposite side members at pointsimmediately adjacent to said frame top member, and

(b) said blade assembly securing means binding element comprises aflexible element.

3. A fire damper assembly comprising in combination,

(a) a rigid rectangular frame including top, bottom and opposite sidemembers which define a main frame plane common to all of said frameforming members and transverse to the air flow path through said frame,

(b) a blade assembly including a plurality of individual damper bladesadjacent ones of which are pivotally interconnected by interfittedhinging elements carried by parallel longitudinally extending bladeedges to effect substantially 180 relative rotation between adjacentblades,

(c) pivot means carried by one blade of said blade assembly andsupported by said frame mounting said blade assembly in said rectangularframe,

(d) means securing the blades of said assembly reversely (folded oneagainst another to form a compacted assembly characterized by thedisposition of the hinge assemblies in planes substantially parallel tothe said main frame plane, said securing .means including a bindingelement and a temperature responsive fusible link disposed about saidblade assembly, and

(e) means including spring means carried by said frame Within the planethereof and engaged with at least one of the blades of said bladeassembly effective to cause said blade assembly to unfold and close theair flow path through said frame by effecting relative rotation betweenadjacent blades of said assembly of substantially 180 whensaid securingmeans is rendered inoperative.

4. A fire damper assembly comprising in combination,

(a) a rigid rectangular frame having top, bottom and side membersdefining a frame main plane transverse to the air flow path through saidframe, said frame having a pair of spaced apart parallel bladeguidingelements extending longitudinally of each of said side members with theblade-guiding elements associated with one side member being parallel toand facing the correspondingly positioned bladeguiding elementsassociated with the other side member to thereby conjointly define apair of facing blade-guidin g trackways,

(b) a blade assembly including a plurality of individual damper blades,each of said damper blades being characterized by a central web and apair of parallel longitudinally extending different hinge elementsdisposed respectively at opposite edges of said web, said hinge elementsbeing of dilferent cross-sectional shape and so formed to interfitwiththe one another to form hinge assemblies that one type of hingeelement .is interfitted with the other type of hinge element on theadjacent one of said plurality of blades to form a composite bladeassembly in which adjacent blades are relatively rotatable through anangle of substantially 180, whereby said blade assembly may be openedout into flat curtain form and may be compacted into a minimum volume byreversely folding adjacent blades of said assembly against one another,said blade assembly being of a length less than the distance between thesaid frame side members to prevent end binding, and being of a widthwhen compacted as aforesaid which is not greater than the distancebetween the said parallel blade-guiding elements associated with eachframe side member,

(c) means mounting said blade assembly in said rectangular frame betweensaid side members, said blade assembly mounting means including pivotmeans carried by the free hinge element of one end blade of said bladeassembly andsupported by said frame immediately adjacent to said frametop member, whereby said blade assembly when compacted is disposedimmediately adjacent to said frame top member and between said frameside members,

(d) means releasably securing the blade assembly in its aforesaidcompacted form with the hinge assemblies disposed in planessubstantially parallel to the frame main plane and between the saidblade-guiding elements, and

(e) spring means carried by said frame within the plane thereof andengaged with at 'least one of the blades of said blade assemblyeffective to open out said blade assembly into its flat form and closethe air flow path through said frame by effecting relative rotationbetween adjacent blades of said blade assembly of substantially 180 whensaid releasable securing means is released.

5. A fire damper assembly comprising in combination,

(a) a rigid rectangular frame having top, bottom and side membersdefining a frame main plane transverse to the air flow path through saidframe, said frame having a pair of spaced apart parallel blade-guidingelements extending longitudinally of each of said side members with theblade-guiding elements associated with one side member being parallel toand facing the correspondingly positioned blade-guiding elementsassociated With the other side member to thereby conjointly define apair of facing bladeguiding trackways, each of said pairs ofblade-guiding elements being vanes pivotally mounted to said frame forswinging movement toward one another about axes parallel to theirlongitudinal extent to thereby reduce the width of the said trackways,

(b) a blade assembly including a plurality of individual damper blades,each of said damper blades being characterized by a central web and apair of parallel longitudinally extending different hinge elementsdisposed respectively at opposite edges of said web, said hinge elementsbeing of different crosssectional shape and so formed to interfit withone another to form hinge assemblies that one type of hinge element isinterfitted with the other type of hinge element on the adjacent one ofsaid plurality of blades to form a composite blade assembly in whichadjacent blades are relatively rotatable through an angle ofsubstantially 180, whereby said blade assembly may be opened out intoflat curtain form and may be compacted into a minimum volume byreversely folding adjacent blades of said assembly against one another,said blade assembly being of a length less than the distance between thesaid frame side members to prevent end binding, and being of a widthwhen compacted as aforesaid which is not greater than the distancebetween the said parallel blade-guiding elements associated with eachframe side member,

(c) means mounting said blade assembly in said rectangular frame betweensaid side members,

(d) means releasably securing the blade "assembly in its aforesaidcompacted form with the hinge assemblies disposed in planessubstantially parallel to the frame main plane and between the saidblade-guiding elements, and a (e) spring means carried by said frame anddrivingly engaged with each of said pairs of pivoted vane blade-guidingelements effective to swingithe latter toward one another as aforesaidto reduce the width of said blade guiding trackways and aid in openingout said blade assembly into flat curtain form to close the air flowpath through said frame by effecting relative rotation between adjacentblades of said blade assembly of substantially when said releasablesecuring means is released.

6. The fire damper assembly as defined in claim 5 further includingauxiliary spring means disposed between at least two adjacent blades ofsaid blade assembly effective to provide an initial blade assemblyunfolding drive when said releasable securing means is released.

7. For use in a folding shutter, a blade assembly comprising a pluralityof individual one piece blades each of which is formed fromsubstantially constant thickness sheet material, each blade including acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full Web length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incrosssection and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, at leastone hinge element of each of alternate blades physically engaging oneanother when said blade assembly is compacted.

8. For use in a folding shutter, a blade assembly comprising a pluralityof individual one piece blades each of which includes a central web anda pair of parallel extending different hinge elements formedrespectively at opposite edges of said web and extending longitudinallycontinuously for substantially the full web-length, one form of hingeelement being interfittable within the other form of hinge element on anadjacent blade by sliding the former endwise intotthe latter, each ofsaid hinge elements being of asymmetric shape in cross-section and wheninterfitted with the other form of hinge element being relativelyrotatable through substantially 180 about an axis non-coincident withthe centroidal axis of either of said hinge elements, whereby said bladeassembly may be opened out into flat curtain form and may be compactedinto a minimum volume by reversely folding adjacent blades of saidassembly against one another, the crosssectional shape of each of saidhinge elements comprising a free end curved section of circularcurvature joined to a straight section which is in turn joined to asecond curve section, the centers of curvature of said first and secondcurved sections being located within the confines of the hinge elementand facing the same surface of the material forming the blade.

9. For use in a folding shutter, a blade assembly comprising :aplurality of individual one piece blades each of which is formed fromsubstantially constant thickness sheet material, each blade including acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full web-length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incrosssection and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centnoidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecross-sectional shape of each of said hinge elements comprising a freeend curved section of circular curvature joined to a straight sectionwhich is in turn joined to a second curved section, the said straightsections of both said hinge elements being substantially the same inlength, the centers of curvature of said first and second curvedsections being located within the confines of the hinge element andfacing the same surface of the sheet material forming the blade.

10. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral Web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said Web and extendinglongitudinally continuously for substantially the full web-length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former end-wise into thelatter, each of said hinge elements being of asymmetric shape incross-section and when interfitted with the other form of binge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into fiatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecrosssectional shape of each of said hinge elements compris ing a freeend curved section of circular curvature joined to a straight sectionwhich is in turn joined to a second curved section, the said straightsections of both said hinge elements being substantially the same inlength and the said curved sections within each hinge element being ofsubstantially the same radius of curvature.

11. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full web-length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incross-section and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecross-sectional shape of each of said hinge elements comprising a freeend curved section of circular curvature joined to a straight sectionwhich is in turn joined to a second curved section, said hinge elementsbeing interfitted so that the centers of curvature of their free endcurved sections are coincident with each other and with the axis ofhinging rotation.

12. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full web length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incross-section and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially about an axisnon-coincident with the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecross-sectional shape of each of said hinge elements comprising a freeend curved section of circular curvature joined to a first straightsection followed by second and third curved sections and a terminatingstraight section which latter joins the hinge element to the bladecentral web.

13. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full web length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incross-section and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecross-sectional shape of each of said hinge elements comprising a freeend curved section of circular curvature joined to a first straightsection followed by a second and third curved sections and a terminatingstraight section which latter joins the hinge element to the bladecentral web, the said first straight sections of both said hingeelements being substantially the same in length, and the free end andsecond curved sections within each hinge element being of substantiallythe same radius of curvature while the third curved section within eachhinge element is of substantially larger radius of curvature than theother curved sections of that hinge element.

14. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said' web and extendinglongitudinally continuously for substantially the full web length, oneform of hinge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incross-section and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident With the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecross-sectional shape of each of said hinge elements comprising a freeend curved section of circular curvature joined to a first straightsection followed by second and third curved sections and a terminatingstraight section which latter joins the hinge element to the bladecentral web, said hinge elements being interfitted so that the centersof curvature of their free end curved sections are coincident with eachother and with the axis of hinging rotation.

-15. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full web-length, oneform of hinge element being interfittable within the other form of bingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asy-mmetric shape incross-section and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centroidal axis of either of said hingeelements, w-hereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecrosssectional shape of each of said hinge elements comprising a freeend curved sect-ion of circular curvature joined to a straight sectionwhich is in turn joined to a second curved section, said hinge elementsbeing interfitted so that the centers of curvature of their free endcurved sections are coincident with each other and with the axis ofhinging rotation, the arcuate extent of the free end curved sections ofboth hinge elements and the length of the straight section of the innerhinge element being such that the free end of the free end curvedsection of the outer hinge element abuts the side of the inner hingeelement straight section at the desired limit of opened out bladerotation to thereby provide a positive stop against further relativerotation between adjacent blades.

16. For use in a folding shutter, a blade assembly comprising aplurality of individual one piece blades each of which includes acentral web and a pair of parallel extending different hinge elementsformed respectively at opposite edges of said web and extendinglongitudinally continuously for substantially the full web length, oneform of binge element being interfittable within the other form of hingeelement on an adjacent blade by sliding the former endwise into thelatter, each of said hinge elements being of asymmetric shape incross-section and when interfitted with the other form of hinge elementbeing relatively rotatable through substantially 180 about an axisnon-coincident with the centroidal axis of either of said hingeelements, whereby said blade assembly may be opened out into flatcurtain form and may be compacted into a minimum volume by reverselyfolding adjacent blades of said assembly against one another, thecrosssectional shape of each of said hinge elements comprising a freeend curved section of circular curvature joined to a first straightsection followed by second and third curved sections and a terminatingstraight section which latter joins the hinge element to the bladecentral web, said hinge elements being inter-fitted so that the centersof curvature of their free end curved sections are coincident with eachother and with the axis of hinging rotation, the arcuate extent of thefree end curved sections of both hinge elements and the length of thefirst straight section of the inner hinge element being such that thefree end of the free end curved section of the outer hinge element abutsthe side of the inner hinge element first straight section at the de-'sired limit of opened out blade rotation to thereby provide a positivestop against further relative rotation between adjacent blades.

17. A blade assembly for a folding shutter comprising a plurality of onepiece blades each of which is formed from substantially constantthickness sheet material, each blade including a central web and a pairof parallel extending hinge elements formed respectively at oppositeedges of said web and extending longitudinally continuously forsubstantially the full web length, one hinge element on one blade beinginterfittable within a hinge element on an adjacent blade by sliding theformer endwise into the latter to form a hinged blade pair, each of saidhinged blades of said pair when interfitted with the other beingrelatively rotatable through a sufiicient angle so that said bladeassembly may be opened out into flat curtain form and may also becompacted into a minimum volume by reversely folding blades of saidassembly against one another, at lea-st one hinge element of each ofalternate blades physically engaging one another when said bladeassembly is compacted.

References Cited by the Examiner UNITED STATES PATENTS 790,632 5/1905Hall -235 X 848,853 4/1907 Reed 160-35 X 1,205,707 11/1916 Cahill160-235 X 1,939,728 12/1933 Spaunburg 16-178 X 2,586,561 2/1952 Poggi160-235 X 2,804,641 9/1957 Zavada 16-128 X 2,992,450 7/ 19 61 Pittenger160-192 X HARRISON R. MOSELEY, Primary Examiner. P. M. CAUN, AssistantExaminer.

17. A BLADE ASSEMBLY FOR A FOLDING SHUTTER COMPRISING A PLURALITY OF ONEPIECE BLADES EACH OF WHICH IS FORMED FROM SUBSTANTIALLY CONSTANTTHICKNESS SHEET MATERIAL, EACH BLADE INCLUDING A CENTRAL WEB AND A PAIROF PARALLEL EXTENDING HINGE ELEMENT FORMED RESPECTIVELY AT OPPOSITEEDGES OF SAID WEB AND EXTENDING LONGITUDINALLY CONTINUOUSLY FORSUBSTANTIALLY THE FULL WEB LENGTH, ONE HINGE ELEMENT ON ONE BLADE BEINGINTERFITTABLE WITHIN A HINGE ELEMENT ON AN ADJACENT BLADE BY SLIDING THEFORMER ENDWISE INTO THE LATTER TO FORM A HINGED BLADE PAIR, EACH OF SAIDHINGED BLADES OF SAID PAIR WHEN INTERFITTED WITH THE OTHER BEING